Balaenoptera omurai 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Balaenopteridae

Scientific Name: Balaenoptera omurai Wada, Oishi & Yamada, 2003
Common Name(s):
English Omura’s Whale
Taxonomic Notes: Although it was only recently described (Wada et al. 2003), the separate species identity of Omura’s Whale is now well established phylogenetically (Sasaki et al. 2006). It was formerly regarded as a pygmy form of Bryde’s Whale, but it is not particularly closely related to that group, lying outside the clade formed by B. musculus, B. borealis, and two forms of Bryde's Whales (called B. brydei and B. edeni in Sasaki et al. 2006). Omura’s Whale is not yet recognized in the IWC Schedule.

To date (January 2007), the genetic identity has been determined for nine specimens. A morphological description is only available for the type specimen (a stranding in the Sea of Japan). Its morphology is quite distinct from those of Bryde’s Whales and other known baleen whales, but its colouration resembles that of the Fin Whale (Wada et al. 2003).

Of the remaining eight genetically identified specimens, six were collected in the Solomon Sea in 1976 under a scientific permit to take Bryde’s Whales, and were reported as unusually small Bryde’s Whales (Ohsumi 1978). The two specimens collected under scientific permit in the eastern Indian Ocean in 1978 were not noticed to be distinct from the Bryde’s Whales that were also collected there at the same time (Ohsumi 1980).

LeDuc and Dizon (2002) genetically analysed specimens of small “Bryde’s Whales” from the Bohol Sea, Philippines, and found that they segregated phylogenetically outside the Sei/Bryde’s Whale clade; from a comparison of the published phylogenies, Sasaki et al. (2006) concluded that these specimens correspond to B. omurai.

The nomenclature is not yet fully settled. Although phylogenetic and morphological analyses demonstrated that B. omurai is distinct from the putative B. edeni specimen of Junge (1950) (collected near Singapore, now held in Leiden, Netherlands), the genetic identity of the type specimen of B. edeni (Anderson 1879; collected 1871 near the Sittang river in Myanmar, now held in Calcutta, India) has not yet been determined; the name may be a senior synonym of B. omurai or of the large-type Bryde's Whale.

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N.
Reviewer(s): Taylor, B.L. & Notarbartolo di Sciara, G. (Cetacean Red List Authority)
The range of this recently described species is poorly known, and no reliable population estimates are available. It is therefore listed as Data Deficient. It is subject to at least some local hunting.

Geographic Range [top]

Range Description:The range of Omura’s whale is poorly known because to date very few specimens have been confirmed. The type specimen was a stranded individual collected near Oyama in the southern Sea of Japan in 1998 (Wada et al. 2003). Eight specimens taken under scientific permit in the 1970s, identified at the time as Bryde’s whales (B. edeni/brydei), were subsequently re-identified genetically from archived tissue samples as B. omurai (Wada et al. 2003, Sasaki et al. 2006).

Six of the B. omurai specimens were taken in deep water in the Solomon Sea in 1976, and reported as unusually small Bryde’s whales (Ohsumi 1978). Two specimens were taken in deep water near the Cocos (Keeling) Islands in 1978, and reported as ordinary Bryde’s whales, which were also collected in the same area (Ohsumi 1980).

Genetic identification confirms the presence of B. omurai in the Bohol Sea, Philippines (see above).

Specimens of B. omurai may have been collected elsewhere without being recognized. Bannister (1964) reported eight “Bryde’s” whales taken off Western Australia during 1958-63 that “do not match the published descriptions of specimens from other parts of the world” but their small size (11.2-11.7 m for mature animals) appears consistent with either B. omurai or the small type of B. edeni/brydei.

B. omurai is at least partially sympatric with Bryde’s whales (B. edeni/brydei), and occurs both in deep water and in inshore areas. The location of the type specimen (Sea of Japan) may not be representative.
Countries occurrence:
Cocos (Keeling) Islands; Indonesia; Japan; Malaysia; Philippines; Solomon Islands
FAO Marine Fishing Areas:
Indian Ocean – eastern; Pacific – northwest; Pacific – western central
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The only population estimate that may relate to B. omurai is an estimate of 1,800 from sightings data for the Solomon Islands “Bryde’s whale” stock (Ohsumi 1980). However, given the small sample size, the use of methodology that is no longer accepted, and the possibility that some of the animals seen may have been B. brydei/edeni, little reliance can be placed on this figure. The global population size is unknown.
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:The diet of B. omurai is not known. Stomach contents apparently were examined for the specimens taken under scientific permit in the 1970s but have not been published separately from those of Bryde’s whales taken in the same expeditions. No prey items other than euphausiids were found (Kawamura 1977). B. omurai occurs in both deep and shallow water, and is at least partly sympatric with Bryde’s whales.

Use and Trade [top]

Use and Trade: This species might have been harvested commercially in the past (probably identified as Bryde's Whale), and is still subject to some local level harvesting.

Threats [top]

Major Threat(s): Because the range of the species is poorly known and has only recently been described, it may have been subject to catching by commercial whaling operations in the past. It may also be subject to by-catch.

Based on genetic identifications (LeDuc and Dizon 2002), it can be inferred that B. omurai have been taken in the Philippines artisanal whale fisheries (Dolar et al. 1994; Perrin et al. 1996), but more analysis would be needed to determine what proportion of the “Bryde’s whales” taken there were in fact B. omurai..

Conservation Actions [top]

Conservation Actions: No specific conservation measures have been taken, but B. omurai will have been an incidental beneficiary of the area restrictions on pelagic whaling that were originally designed to protect the low-latitude winter breeding grounds of other baleen whale species (Tønnessen and Johnsen 1982). The species is on Appendix I of CITES.

Citation: Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Balaenoptera omurai. The IUCN Red List of Threatened Species 2008: e.T136623A4319390. . Downloaded on 16 August 2018.
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